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Dim light at night found to prevent effectiveness of tamoxifen

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Tamoxifen is one of the cheapest and most effective treatments for breast cancer. Melatonin, a hormone produced during sleep, has been found to be necessary for tamoxifen to work. Steven Hill and David Blask from Tulane University School of Medicine reported this discovery in the July 24, 2014, edition of the journal Cancer Research.

Tamoxifen is the world’s largest selling hormonal drug for the treatment of breast cancer. The drug works effectively in premenopausal women and in postmenopausal women. Tamoxifen has also been approved by the U. S. Food and Drug Administration for the prevention of breast cancer.

The researchers studied the effects of tamoxifen on rats that had cancer. The rats were exposed to a series of 12 hour periods of light and dark while taking tamoxifen. The rats that were exposed to even a dim amount of light during the dark phase of the experiment that represented sleep in humans had a 2.6 higher rate of breast cancer growth. The researchers also proved that artificially induced levels of melatonin that were high prevented the cancer suppression effect of tamoxifen but do not recommend supplementation in humans.

The researchers determined that the absence of the hormone melatonin caused by the presence of light during sleep made tamoxifen ineffective. The amount of light needed to eliminate the effectiveness of tamoxifen was similar to the amount of light that would be seen though the crack at the bottom of a door. Sleeping in front of computer screen or a television also prevent tamoxifen from binding with the estrogen receptors on cancer cells that need estrogen for growth.

The expectation of this discovery is the reduction of breast cancer growth in women that have breast cancer and the potential to prevent breast cancer in women that have a familial history of breast cancer. The caveat is that the women do not have any light while they sleep. One should expect a class action law suit against the various manufacturers of tamoxifen by women who had breast cancer recur while taking tamoxifen and the relatives of women that died while taking tamoxifen because “The manufacturers should have known about the new research.”

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